The growth of the gate oxide layer is a critical step in manufacturing semiconductor devices, particularly miniaturized semiconductor devices. Thin gate oxide layers free of defects and of high quality without contamination are essential for proper device operation. As design rules shrink to the submicron range for ultra large-scale integrated circuit (ULSI) semiconductor device, it becomes increasingly vital to grow gate oxides on crystalline silicon at a reduced thickness with good electrical characteristics and long-term reliability in a repeatable manner. Various oxidation techniques have been developed and practiced, including dry oxidation, dry oxidation with HCl, sequential oxidation using different temperatures and ambients, wet oxidation, deduced pressure techniques, and high pressure/low temperature oxidation. The drain current in a MOS transistor is inversely proportional to the gate oxide thickness. However, it is extremely difficult to form a gate oxide layer with a reduced thickness, e.g., about 15 .ANG. to about 30 .ANG. with higher oxide breakdown and higher reliability.
Therefore, there exists a need for an efficient and production worthy method for manufacturing semiconductor devices comprising transistors with very a thin gate oxide.